Nanomechanical Characteristics between Typical Components of Crude Oil and Monominerals of Sandstone

One of the major challenges during the development of low-permeability sandstone reservoirs is the interaction between the oil and rock, which makes it difficult to displace the oil in the nanoscale pores of the formation rock. This study investigates the interaction between typical crude oil components, such as chain alkyl, sulfonic acid group, and carboxyl group, and representative sandstone monominerals, including quartz, albite, and potassium feldspar in the aqueous phase with different salinities by using the nanomechanical method. The maximum adhesion strength measured in this study is 768.75 nN μm–2, which is the adhesion strength between the carboxyl group and quartz in simulated formation water, and it is 9.2 times higher than that of the sulfonic acid group and albite in deionized water. Experimental results show that the high concentration of cations in the formation water enhances the adhesion strength between the polar components of crude oil and sandstone monominerals, resulting in strong attractive forces. Furthermore, it is found that the dominant components responsible for this strong interaction are the carboxyl group and quartz. In addition, the results show that the intensity and range of adhesion strength caused by the high-valent cations, such as Mg2+, Ca2+, and Al3+, are larger than those of the low-valent cations, such as Na+ and K+, and increase with increasing ion concentration. By accurately quantifying the interaction between typical components of crude oil and sandstone monominerals, this study reveals the adhesion mechanism of crude oil in low-permeability sandstone reservoirs, which provides a theoretical basis for the efficient displacement of oil.